About Tic Tac Toe

Tic Tac Toe is one of the oldest known pencil-and-paper games. Variants have been played for thousands of years — scratches in the form of a three-by-three grid have even been found carved into the ruins of the Roman Empire. The modern name appeared in English in the 19th century, and the game became a staple of childhood worldwide.

Despite its simplicity, Tic Tac Toe has been a favorite subject for game theorists and computer scientists. With perfect play from both sides, the game is a forced draw — a result that has been used to teach minimax search and basic AI for decades. This version includes AI difficulty settings, larger 4×4 and 5×5 boards, and a two-player mode for local matches.

How to Play

Controls: Click or tap any empty cell to place your mark. X always moves first. Switch between AI and two-player mode, adjust AI difficulty, and pick a board size from the settings at the top.

Objective: Be the first to line up three marks in a row — horizontally, vertically, or diagonally. On larger boards the required line length adjusts automatically. A full board with no winner ends in a draw.

Tips & Strategy

• On the 3×3 board, always take the center if you go first. It is part of the most winning lines.
• If the opponent takes the center, respond with a corner — never an edge.
• Look for forks: positions where you threaten two different three-in-a-rows at once.
• Always block the opponent's immediate three-in-a-row before making your own move.
• On larger boards, think in terms of open lines rather than individual cells. Control long diagonals early.